Field of the Invention
The present invention relates to a unit moving apparatus that moves a unit with respect to a main body and an image forming apparatus including the unit moving apparatus.
Description of the Related Art
Conventionally, an image forming apparatus such as a printer, and a copying machine is provided with a unit that can be slid and pulled out from a main body of the image forming apparatus for sheet replenishment, removal of a sheet jammed in transportation, or various types of maintenance. After the unit is slid and pulled out, the unit is re-attached to the original position. At this time, a load is applied between the pulled unit and the main body from various units, such as a contact release unit of each component, and positioning unit, when the unit is moved in an attachment direction.
In many cases, since the attachment of the unit is manually conducted by the user, insufficient attachment may occur because of the load, and the insufficient attachment of the unit can give rise to image quality degradation. Furthermore, operability at the time of the attachment of the unit is degraded.
In view of the foregoing situation, some conventional apparatuses are equipped with a unit pull-in mechanism assisting in the attachment of the unit to improve the unit attachment reliability and reduce operational force (refer to Japanese Patent Application Laid-Open No. 2012-101888). The unit pull-in mechanism requires sufficient pulling force to automatically and surely pull in the unit to the attachment completion position against the load applied to the unit during the attachment.
The load applied to a sheet feeding cassette during the attachment of the sheet feeding cassette to a main body will be described below. The sheet feeding cassette is an example of a unit to which a load is applied when the unit is pulled in. The sheet feeding cassette stores sheets therein and is provided so as to be attachable to and detachable from the main body of the image forming apparatus. A positioning unit is provided between the sheet feeding cassette and the main body because the sheet feeding cassette needs to be attached to an appropriate position in the main body of the image forming apparatus. For example, in general, the positioning unit is configured to perform the positioning by fitting a fitting boss into a fitting hole. In such a configuration, resistance generated when the fitting boss is fitted into the fitting hole becomes the load applied when the sheet feeding cassette is pulled in.
Further, in a case where a sheet stacking portion that is provided to the sheet feeding cassette and on which sheets are stacked is lifted by driving of a motor provided to the main body of the image forming apparatus, the driving of the motor needs to be transmitted to a lifter tray provided on a lower side of the sheet stacking unit. In this case, a driving gear of the main body is meshed with a driven gear connected to the lifter tray while the sheet feeding cassette is being pulled in. Accordingly, when the gears are meshed together, a load is applied to the sheet feeding cassette.
Furthermore, the sheet feeding cassette receives loads from various other units besides the foregoing units when the sheet feeding cassette is pulled in. In many cases, such e units that generate the loads are arranged not evenly but unevenly due to the positional relationship between the main body of the image forming apparatus and the unit.
If the load that is applied when the sheet feeding cassette is pulled in is not even, a rotation moment occurs in the sheet feeding cassette, the sheet feeding cassette is inclined, and the sheet feeding cassette being inclined is pulled in. As a result, the load further increases, so the pulling force of the unit pull-in mechanism needs to be set large. However, when the pulling force of the unit pull-in mechanism is set large, a large force is required to pull out the sheet feeding cassette from the attachment completion position, so that operability is degraded.
In response to the foregoing problem, a technique has been discussed in which two points of action, at which a large resistance force mainly becoming the load is strongly applied are located, and the position of a unit pull-in mechanism is specified with respect to the points of action, so that the generation of a rotation moment is minimized (refer to Japanese Patent Application Laid-Open No. 2011-37629).
However, in a case where there is a plurality of units that generate loads when the unit is pulled in, it is sometimes difficult to realize an optimum arrangement as discussed in Japanese Patent Application Laid-Open No. 2011-37629. Further, in a case of a compact product, units that generate a resistance load are often disposed unevenly with respect to the main body of an apparatus. In such a case, it is sometimes impossible to dispose the unit pull-in mechanism in the vicinity of the units. Consequently, an increase in a load associated with generation of a rotation moment has been difficult to avoid with devising the disposition.
Furthermore, due to operational constraints of the units, the loads are often generated at different time points during the attachment of the unit. In such a case, there exist limitations in preventing generation of a rotation moment merely by devising the disposition.